[Haskell-cafe] problem reading /proc/interrupts with ByteString

[Matthew Brecknell]

Leandro Lisboa Penz:
> I'm having some problems using ByteString.Char8.readFile to read 
> "/proc/interrupts". I reads nothing. I guess maybe that's because the 
> file is sort of special, but I could read it by opening and using 
> ByteString.Char8.hGetContents.

ByteString.Char8.readFile uses hFileSize to determine the buffer size to
use:

> readFile f = bracket (openFile f ReadMode) hClose
>     (\h -> hFileSize h >>= hGet h . fromIntegral)

Now, if you look at the size of /proc/interrupts, as reported by ls, you
should see the problem.

By contrast, ByteString.Char8.hGetContents determines the required
buffer size by reading to the end of the file.